(a) Field of the Invention
This invention relates to the imprinting of images and artwork on clear transparent photostencil films and more particularly, but not by way of limitation, a process using a computer and thermal printer to create and imprint digital images and/or artwork on photostencil films. This process does not require added steps in creating camera ready artwork or a photo positive or negative for screen printing. The integral technique of the subject process provides for an efficient and economical means to process photostencil films for application to a clean screen mesh.
(b) Discussion of Prior Art
Heretofore, one process commonly used in the screen printing industry includes the applying of a liquid emulsion directly to a screen mesh mounted on a frame. The emulsion is allowed to dry. Artwork in the form of a positive or negative film, which is generated in a dark room, is then laid on the screen and exposed to a light source. The artwork is then removed. The screen is washed until the image is removed from the emulsion layer left from the artwork on the screen. The screen is dried and ink is applied through the image imprinted on the screen mesh.
A problem with the direct emulsion process is an operator is quite often unable to control the amount of emulsion applied on the screen. Therefore the various thicknesses of the emulsion layer cause color changes and associated problems. Also, any major problems related to ultraviolet light exposure on the emulsion layer may require the complete removal of the emulsion layer from the screen mesh. This procedure is time consuming and reduces the useable life of the screen mesh. Further, any foreign material or particles in the air will adhere to the emulsion causing spots and imperfections on the image requiring corrections by hand. Still further, the operator using this type of process may delay applying the emulsion to the screen until the artwork has been delivered and ready for processing.
Another common process used in screen printing includes applying a capillary or direct photostencil film on a screen mesh. Water is applied on the screen with an emulsion side of the direct film laid on top of the water surface. The excess water is removed and the direct film and screen are allowed to dry. Artwork such as a positive or negative film, which is generated in a dark room, is then laid on the direct film on the screen and exposed to a light source. The emulsion side of the direct film reacts to the image on the artwork. The artwork is then removed. The screen is washed until the image from the artwork is removed from the emulsion side of the direct film. The screen is dried and ink is applied through the image imprinted on the screen mesh.
A drawback in using the capillary or direct photostencil film is the requirement of having to use a vacuum table to draw the art work close to the face of the screen mesh. This procedure can be awkward due to the screen frame impeding the vacuum draw. Also, any foreign material or particles on the direct film or screen mesh will adhere to the emulsion causing spots and imperfections on the image requiring additional time to make corrections by hand. Further, washout when using direct film is difficult to control because no image background or color barrier is there to differentiate the removal of the emulsion layer on the film.
Still another common process in the screen printing industry is the use of indirect photostencil film. Artwork is generated in a darkroom using a separate photographic process to create a positive or negative. The indirect photostencil film and photonegative or positive is exposed to light and an image is imprinted on the emulsion side of the film. The image on the emulsion side is then washed out with water. The photostencil film is applied to a screen mesh and washed. Excess water removed from the screen mesh and the screen and film are allowed to dry. The clear base film is then removed leaving the emulsion layer and image imprint on the screen mesh. Ink is applied to the screen and the ink comes through the voided area's of the image on the screen mesh.
An obvious problem of the above mentioned screen processes when using either direct or indirect film is a dark room is required to develop a positive or a negative. The subject process eliminates the need of dark room generated film.
In U.S. Pat. No. 4,940,993 to Sato, an image recording apparatus using heat sensitive film and a thermal recording head is disclosed. This device is used in convection with a microcomputer. In U.S. Pat. No. 4,596,993 to Erlichman a thermal recording system is described that records on a film and is controlled by digital signals. U.S. Pat. No. 5,274,395 to Mizoguchi et al. describes using ink sheets with a thermal transfer system. The system is controlled by an image processing unit. U.S. Pat. No. 5,291,220 to Klees describes the use of a complex computer controlled thermal printer. The printer is designed to print a continuous tone image. U.S. Pat. No. 5,280,305 to Monroe and U.S. Pat. No. 5,149,613 to Stahlhofen et al. describe different types of thermal printing wherein a system is computer controlled for supplying signals from memory.
None of the above mentioned patents describe or teach a process for turning computer generated digital artwork into a screen printing image using a thermal image printer applied to photostencil film.